smoothScroll.js

        function SmoothScroll(target, speed, smooth) {
            if (target == document)
                target = (document.documentElement || document.body.parentNode || document.body) // cross browser support for document scrolling
            var moving = false
            var pos = target.scrollTop
            target.addEventListener('mousewheel', scrolled, false)
            target.addEventListener('DOMMouseScroll', scrolled, false)

            function scrolled(e) {
                e.preventDefault(); // disable default scrolling
                var delta = e.delta || e.wheelDelta;
                if (delta === undefined) {
                    //we are on firefox
                    delta = -e.detail;
                }
                delta = Math.max(-1, Math.min(1, delta)) // cap the delta to [-1,1] for cross browser consistency

                pos += -delta * speed
                pos = Math.max(0, Math.min(pos, target.scrollHeight - target.clientHeight)) // limit scrolling

                if (!moving) update()
            }

            function update() {
                moving = true
                var delta = (pos - target.scrollTop) / smooth
                target.scrollTop += delta
                if (Math.abs(delta) > 0.5)
                    requestFrame(update)
                else
                    moving = false
            }

            var requestFrame = function() { // requestAnimationFrame cross browser
                return (
                    window.requestAnimationFrame ||
                    window.webkitRequestAnimationFrame ||
                    window.mozRequestAnimationFrame ||
                    window.oRequestAnimationFrame ||
                    window.msRequestAnimationFrame ||
                    function(func) {
                        window.setTimeout(func, 1000 / 50);
                    }
                );
            }()
        }

// call it 

new SmoothScroll(document, 120, 12)

Hi, thanks for this great plugin, Im having some problems with anchor scroll smooth, when i click on link anchor and scroll the page brings back to top. I tried many ways to fix this but without success, can you help me?

this is my scroll anchor plugin:

var links = document.getElementsByClassName('scroll-link');

for (var k = 0; k < links.length; k++) {
links[k].onclick = scroll;
}
function scroll(e) {
e.preventDefault();
var id = this.getAttribute('href').replace('#', '');
var target = document.getElementById(id).getBoundingClientRect().top;
animateScroll(target);
if(document.querySelector('.sandwich-trigger').classList.contains('sandwich-open') == true) {
document.querySelector('.menu ul').classList.remove('nav-open');
document.querySelector('.sandwich-trigger').classList.remove('sandwich-open');
}
}
function animateScroll(targetHeight) {
targetHeight = document.body.scrollHeight - window.innerHeight > targetHeight + scrollY ?
targetHeight : document.body.scrollHeight - window.innerHeight;
var initialPosition = window.scrollY;
var SCROLL_DURATION = 40;
var step_x = Math.PI / SCROLL_DURATION;
var step_count = 0;
requestFrame(step);
function step() {
if (step_count < SCROLL_DURATION) {
requestAnimationFrame(step);
step_count++;
window.scrollTo(0, initialPosition + (targetHeight - 70) * 0.25 * Math.pow((1 - Math.cos(step_x * step_count)), 2));
new WSmoothScroll(document.body,120,12, targetHeight, initialPosition, step_x, step_count);
}
}
}